- The probability of drawing a red marble is \( \frac{1}{6} \).
- The probability of drawing a marble that is not red is \( \frac{5}{6} \).
- The probability of drawing a marble with the number 3 written on it is \( \frac{1}{8} \).
Thus, the final answers are:
\[
\boxed{P(\text{Red}) = \frac{1}{6}, \quad P(\text{Not Red}) = \frac{5}{6}, \quad P(\text{Number 3}) = \frac{1}{8}}
\]